1. Field of the Invention
The present invention relates to an ink-jet recording medium that can be suitably used in an ink-jet recording process. More particularly it relates to a recording medium having superior absorption properties and color-forming performance for a water-based ink, and also capable of achieving a superior sharpness of recorded images obtained.
The present invention also relates to an ink-jet recording medium capable of providing recorded images that may cause less indoor color changes and have a good storage stability.
The present invention still also relates to an ink-jet recording method making use of such a medium.
2. Related Background Art
Hitherto known recording mediums used for ink-jet recording include;
(1) those comprising an ordinary paper mainly composed of pulp, so made as to have a low degree of sizing as in filter paper or blotting paper; and PA0 (2) those comprising a substrate paper and a coating layer provided thereon using a pigment such as silica or zeolite, which is porous, has a large oil absorption and is capable of adsorbing a coloring component contained in ink, as disclosed in Japanese Patent Application Laid-open No. 56-148585.
Meanwhile, in an ink-jet recording system that forms a color image with a high quality level and a high resolution, there is a demand for a particularly good image storage stability. Because of such a demand, methods of improving resistance to the fading of images due to sunlight, visible light, ultraviolet light, etc. are known in the art (see, for example, Japanese Patent Applications Laid-open No. 60-49990 and No. 61-57380).
Recently, however, the problem of image storage stability concerning indoor color changes of recorded images has been highlighted as a problem peculiar to coated papers.
The fading of images that has been hitherto questioned is a phenomenon caused when dyes present in recorded images are decomposed because of irradiation with visible light or ultraviolet light. This does not occur at the place not exposed to direct sunlight. At the place exposed to direct sunlight, this is a problem of fading that may arise also in respect of images recorded on what is called PPC paper, commonly available, and recording mediums of the types of any of the above (1) and (2).
The indoor color changes referred to in the present invention do not occur on non-coated paper such as PPC paper, and hence the problem of indoor color changes is peculiar to coated paper. Thus, this can be considered to be a problem greatly caused by a pigment that forms a coat layer.
In general, the indoor color changes can be inhibited in a recording medium having a coat layer comprised of a pigment having a small specific surface area as exemplified by calcium carbonate or kaolin. When such a pigment is used, however, the pigment can not trap a dye because of its small specific surface area, so that resulting images may have a low density and can not be images with a high image quality. On the other hand, in the case of recording mediums having a coat layer comprised of highly active silica with a large specific surface area, it has been possible to obtain images with a high density but impossible to inhibit indoor color changes.
Japanese Patent Laid-open Application No. 64-75280 discloses a recording medium containing an aluminum oxide. In such a recording medium, the resistance to indoor color changes can be improved to a certain extent, but still has been unsatisfactory.
Moreover, in an instance in which pigments of different kinds are mixed to form a coat layer, either image density or resistance to indoor color changes has been unsatisfactory.
Japanese Patent Application Laid-open No. 1-108083 discloses a recording medium comprising dual ink-receiving layers, wherein aluminum oxide is used together in its surface layer so that image density can be improved. There, however, a limitation on the amount of the aluminum oxide taking account of the inhibition of indoor color changes, so that the density of resulting images has been unsatisfactory.
Namely, in conventional techniques, an attempt to make image density and image quality level higher brings about indoor color changes, and on the other hand an attempt to inhibit indoor color changes results in a lowering of image density. These conflict with each other, and have been considered incompatible.